PROBLEMS OF TECHNOLOGICAL PROCESSING OF HIGH-SILICON PHOSPHATE ORES

The known classification of phosphate ores, including their division by types, kinds and subtypes, allows to identify common patterns and approaches to the processes of their enrichment and technological processing. When forming a classifier of raw materials, the most significant parameters that play a key role at individual stages of its processing are highlighted. For example, the criterion of technological suitability of raw materials for sulfuric acid extraction was the regulated mass ratio of impurities (CaO, MgO, Fe2O3, Al2O3, CO2, F, н. o.) to the target component (P2O5). Thus, the choice of standard raw materials - Khibiny apatite concentrate (AK) for the production of EFC was justified. Alternative methods of processing into phosphorus-containing fertilizers were used for raw materials from other deposits due to the increased content of impurities. High-siliceous phosphorites characterized by a share of acid-insoluble residue (ins.r.) were considered unsuitable for technological processing. They were subjected to mechanical activation and used as a slow-acting fertilizer. The type of siliceous component of phosphorites was not given sufficient attention. Systematic studies of the composition, structure and properties of various types of phosphate raw materials allowed us to conclude that this aspect must be taken into account, since the SiO2 impurity can be in the form of alpha-quartz and/or aluminosilicates. The presence of the latter in aqueous suspensions, unlike alpha-quartz, leads to gradual swelling, changes in structure, deterioration of the rheological characteristics of reaction systems and problems of transportation in the industrial scheme. The values of viscosity (η) of the intact and destroyed structure of the flow of nitric acid suspensions based on standard raw materials (AK), based on which the vast majority of industrial process flow diagrams are designed, and two types of phosphorites from the Polpinsky and Kyzylkum deposits (PF and KyzF, respectively) are presented. Alpha-quartz dominates in the composition of the first of them, and aluminosilicates dominate in the second. It is shown that the viscosity values of the reaction masses at 25 °C differ by a factor of several times and are 400 for AK, 800 for PF, and 1100 mPa·s for KyzF. Increasing the temperature to 55 °C allows to bring the viscosity of reaction systems based on PF to a technologically acceptable standard, and the isolation of the inert component (alpha-quartz with high layer porosity and incompressible sediment structure) from the reaction mass upon reaching the raw material decomposition coefficient of 99.7±0.2 wt. % seems to be less energy-consuming in comparison with KyzF.